Cable modem shopping tips

If you're looking for the best home broadband speeds, cable internet service is still the go-to choice since fiber optic is only available in limited areas. But what many people don't know is that they may be paying more than they need to for cable broadband -- especially if they use equipment provided by the cable company.

Indeed, many users can save upward of $10 per month on their current cable internet service. To that end, I've boiled things down to the seven most popular questions I generally receive from readers on the subject of cable internet. I've included in-depth answers to each, including suggestions on how to save on your monthly bill (spoiler: buy your cable modem, don't rent).

Whether you're a current cable internet customer or you're thinking of switching, this Q&A should set you up to get the most for your broadband buck.

The back of a typical DOCSIS 3.0 cable modem. Note the LAN port (top) and the coaxial port.
Dong Ngo/CNET

Is my Comcast Gateway a modem?

No, it's a combo modem/router device.

A modem can only connect a single device to the internet. In order to connect more devices in a home -- many of them are Wi-Fi devices, like your tablets or your laptops -- you also need a Wi-Fi router. To make it simple, most service providers combine a modem and a Wi-Fi router into a single box and call it a gateway. The most popular gateway is the Comcast XB3, which has recently been renamed to Xfinity xFi Wireless Gateway.

Should I get a router/modem combo or two separate devices?

Unless the combo device is provided for free (not likely), or if you're a Comcast customer and you like the new xFi features, always get a standalone modem and a separate router. After getting the modem, just pick up one of these routers or Wi-Fi systems according to your needs. Once the modem is activated, just connect its network port to the WAN (internet) port of a modem and you have a "gateway."

Getting a separate router and modem gives you a lot of flexibility because if you want to upgrade your home network to have faster speed or more features, you just need to replace the router. Or when you want to upgrade your broadband speed, you just need to upgrade the modem. What's more, most routers on the market have more settings and features than the router part of a combo device.

Networking vendors recently have been making combo boxes, and most of them are better than the ones provided by the service providers. If you have to get a combo box for the sake of being tidy, get one of those. At least it will save you the $10/month rental fee. Generally, however, if you have a small office, it's best to get a separate modem and a router.

Which cable modem should I get?

Get one that's capable of delivering at least the speed of the broadband data plan to which you subscribe. For example, if you pay for a plan that promises 100Mbps for download speed, getting a modem that's capable of delivering more than that won't do you any good, unless you plan to upgrade your internet speed later. It doesn't hurt to get a highly capable modem, either, if the price is good. Most current modems on the market can deliver much faster than a overage broadband speed, so in most case you just need to pick the least expensive one.

More on home networking

Modems are generally very simple devices and work the same. The biggest difference between them is the standard they support, which determines the internet speed capacity they are capable of delivering. This standard is called "data over cable service interface specification," or DOCSIS, and currently they all use DOCSIS version 3.0. (Those using DOCSIS 2.0 or earlier are obsolete.) That said, when looking for a modem, make sure you first check to make sure it's on your provider's approved list; examples of such lists are this list from Comcast and this one from Time Warner Cable.

Your actual internet connection speed depends on the speed of the modem, the router, the Wi-Fi connection, switches, the connected client itself and the broadband data plan you pay for, and whichever is the lowest at a given time. For most homes, the broadband speed tends to be the lowest common denominator.

In a typical cable-internet-based home network, you connect the modem to a Wi-Fi router's WAN port using a (preferably) short network cable, to share the internet connection with multiple devices.

Dong Ngo/CNET

New, used or refurb?

It never hurts to buy a brand-new modem, or router, but you can save quite a bit and lose nothing if you go for a used or refurbished one.

Cable modems are simple devices, and once set up, they remain in one place. You never have to change any settings or customize anything at all. There are also no moving parts inside modems (most of them don't even have ventilation fans). For this reason, they can work for a long time and tend to become obsolete before they actually stop working. This means that getting a brand-new modem gives you no more benefits than getting a refurbished one of the same type. Most refurbished modems (and networking devices, for that matter) are just items returned from buyers for cosmetic reasons or which are no longer needed. On the inside, they are the same as a new one. On the market, refurbished modems cost as little as two-thirds of the price of the new unit.

Used modems might come with a little higher risk, depending on the previous owners, since the item might have been abused, or the owner didn't deactivate it with their account (in which case you'll have to get on the phone with the provider to solve that before you can activate it on your account). That said, if you buy a used one, make sure you can return it after a few days, because if it will work for a few days without a problem, chances are it will work for a long time. The major benefit here is that a used modem tends to run about a third of the price of a new one. In my personal experience, the part of a modem that tends to break down first is the power adapter, which is quite easy to replace.

The back of a cable internet combo device. Note the multiple LAN ports and the lack of a WAN port found in a typical router.

Dong Ngo/CNET

I have a modem/router combo device, how do I upgrade my Wi-Fi speed?

You can upgrade your Wi-Fi speed by getting a separate access point (AP) with faster Wi-Fi standards. If you have a small home, all you have to do is connect the new AP to one of the existing gateway's LAN port. After that it's recommend that you disabled the gateway's Wi-Fi which can be done via its web interface.

If you have a large house, you can run a network cable to a distant part of the house and place the new APe there. This way, you won't need to turn off the gateway's Wi-Fi and will have a larger Wi-Fi network. If running a network cable is too much work, you can try a pair of power line adapters.

Should I buy an extended warranty?

Not at all. Cable modems (or combo devices) -- even refurbished ones -- generally come with a factory warranty ranging from 90 days to a year. Since these are simple devices, if anything unusual should happen -- let's say you get a defective unit -- you'll run into issues when setting it up or after just a few days of operation. After that, it's likely that nothing will happen.

That said, buying an extended warranty is just a waste of money. Instead, you should use that money to buy a power surge protector for your home-network devices since lighting and power surges are the two most common causes of damage for this type of equipment. You should also leave the device in an open and dry area to avoid water damage or overheating.

Also note that, if the modem does break down, it's much faster to get a replacement yourself. The warranty process can take days, if not weeks, and during that time, you're offline. So if you really want to make sure you're always connected to the world, get a second (used) modem as a spare.

Should I try to bargain?

Definitely.

It's true that most of us live in an area that's served by just one cable company, but there are alternatives, such as FIOS, satellite, or DSL (which is ubiquitous and generally cheaper). You should use these as your leverage with the cable company for a better deal. You can also get deals by subscribing to multiple-service packages, such as TV, internet, and phone, though don't subscribe for what you're not planning on using.

Some cable companies, such as Comcast, tend to give you good rates for a promotional period, say six months, and then start charging you the full rate, which is up to 50 percent higher. You can always call in when this period ends and ask for another promotional period, or you can just quit and resubscribe. This doesn't cost anything, and you already have the modem.

Most importantly, check with them once in a while when there are new promotions, or just simply call in to ask for a lower rates. It works. After all, you can't get what you don't ask for.